The present invention relates to a bi-directional shift register capable of easily changing the direction of data transfer, which can be used in solid-state image pickup and liquid crystal display devices.
A shift register has a wide range of application. For instance, a shift register may be used in a solid-state image pickup device. In such a device, the shift register can be employed as a horizontal scanning shift register and a vertical scanning shift register to read picture element signals in a scanning mode that are produced by photo-electric conversion elements. The shift register may also be used in a liquid crystal display unit. Here, the shift register is employed as a scanning register for applying a predetermined voltage to liquid crystal display elements corresponding to picture elements.
In the field of image processing, graphic design has become quite popular. For example, when picture element signals are produced by a solid-state image pickup device and displayed on a television monitor, the arrangement of the picture elements can be changed from the original optical image of the object or the arrangement of the picture element signals for the formation of an image can be changed, so that a different image is displayed on a liquid crystal display unit.
In a conventional shift register, the transfer speed can be adjusted by changing the frequency of the data transferring clock signal, or the data length can be adjusted by changing the number of transfer elements. However, the conventional shift register does not have the capability of changing the direction of transfer. Therefore, the shift register in the solid-state image pickup device or in the liquid crystal display unit serves merely as input/output drive means. That is, in the aforementioned field of image processing and graphic design, the solid-state image pickup device or the liquid crystal display unit operates merely as means for outputting or inputting picture element signals. Additional means are then necessary, such as a signal processing circuit or a computer program, to perform all the remaining data processing operations.
Accordingly, a great burden is placed upon the computer program or the signal processing circuit. In addition, the additional means may result in an increase in size and/or in manufacturing cost of the video equipment. Hence, the provision of the additional means may not be feasible. Therefore, the video equipment without the additional means cannot provide many graphic designs.
There has, however, been a strong demand in the art to process and produce images of all kinds of graphical designs.
A shift register that can transfer data not only in the forward direction but also in the reverse direction can meet such a demand. Moreover, such a shift register will have a variety of applications.